1946-1949 Early Hydra-Matic Transmission Fluid

[Cadillac Jack 82]

Personally Dex/Merc III work fine with the gals.  Had a hard shift in the 55 but added some Lucas and boom...gone.

[Michael Brittan CLC #2750]

The ATF transfusion took place as planned.  The transmission took 12.5 quarts of the Dex/Merc, just like the shop manual says it should.  I have only managed to put a few miles on the car since.  My initial impression is that there is a small improvement in the 2-3 shift, but more extensive driving is required when time and weather permit. I'll report again when I have racked up some more miles.

[Michael Brittan CLC #2750]

Latest update:  After a few more miles on the road, my initial impressions following the ATF transfusion remain - i.e. a small improvement.  Tim's observation that Lucas treatment fixed the hard shift on his '55 is interesting, and may be worth trying, though possibly counterintuitive.  I would expect the Lucas additive to increase the viscosity (as per TJ Hopland's post) and therefore maybe exacerbate a hard shift.  On the other hand, maybe a slightly more viscous fluid might slow down the mechanical transition involved in the 2-3 shift and therefore be of benefit.  Any words of wisdom before I try this?

[TJ Hopland]

I don't think we know if the issues is its too thick or too thin for the hydraulic parts or if its too sticky or too slippery for the clutch and band parts so you just have to try both and see which helps. I think that is one of the interesting things about ATF, it kinda has to be all 4 things at the same time.

[Upnorth]

Hello Everyone I was just reading on here about the transmission to carb linkage Adjustment my 47 seems to shift at a slow speed

I was wondering if any one knew do I make the rod shorter or longer to increase the rpm the transmission shifts at?

Thanks Kindly Al

[Michael Brittan CLC #2750]

Al, if you Google "Early Hydramatic changing shift points" you will find references to the question in many threads.

On my ATF experimenting, I'm planning to try the Lucas additive late next week.  I'll report back.

[Michael Brittan CLC #2750]

After further driving, I conclude that the Lucas additve made no detectable difference, but that changing the transmission fluid resulted in a small improvement in the 2-3 shift.  I would say the shifting is now reasonably smooth and acceptable.  Any further refinement would likely take someone with good experience with band adjustment.